The proposed studies will retrospectively examine the role of familial risk in the neuropsychological abilities of elderly individuals with a positive family history for progressive dementia (FHPD+). The FHPD+ subjects will be recruited from the existing cohort of nondemented elderly subjects from the National Alzheimer's Disease Research Center (ADRC) of the University of California, San Diego (UCSD), School of Medicine, Retrospective analyses of neuropsychological abilities will be performed on behavioral data gathered from these individuals. FHPD+ subjects will be identified by medical/family history interviews obtained by the ADRC, and will be group-matched and compared to nondemented elderly from the ADRC who have not identified a family history for dementia (FH). Furthermore, an additional cohort of normal elderly individuals will be recruited from the community for prospective analyses. These subjects will be identified as first-degree relatives of autopsy-confirmed AD patients who have been examined by the Neuropathology Core of the ADRC (i.e., subjects with a positive family history for "definite" Alzheimer's disease; FHAD+). These FHAD+ subjects will be recruited in an effort to employ more rigorous methods in identifying familial risk. Along with tests selected from the neuropsychological battery normally given to ADRC subjects, a novel battery of clinical and experimental neuropsychologic tests of sustained and divided attention, as well as tests designed to quantify strategy use in problem-solving and memory, and will be administered. The proposed studies will extend our knowledge of the neuropsychologic characteristics of very early DAT, and help to determine whether preclinical cognitive markers exist in certain genetically susceptible individuals at risk for the development of Alzheimer's disease.